Incandescent electric lamp



y 1936. c. H. BRASELTON 2,039,773

INCANDESCENT ELECTRIC LAMP Filed May 17, 1932 INVENTOR Patented May 5, 1936 UNITED STATES PATENT OFFICE INCANDESCENT ELECTRIC LAMP Chester H. Braselton, New York, N. Y., asslgnor to Sirian Lamp Company, Newark, N. .L, a corporation of Delaware This invention relates to incandescent electric lamps and has for its principal object the provision of means to increase the life of such a lamp.

Another object of the invention is to provide an incandescent electric lamp in which there is a ballast to prevent the filament from becoming overheated due to surges of current.

Still another object of the invention is to provide a lamp with means to prevent arcing between the filament and supporting leads which might result in deterioration of the filament and consequent burning out.

Other objects of the invention and objects relating particularly to the method of constructing and assembling the various parts will be apparent as the description of the invention proceeds.

The invention has been illustrated in the accompan'ying drawing in which: as Fig. l is a perspective view partly in section of a lamp embodying the invention;

Fig. 2 is an enlarged detail view partly in section of the filament used in the lamp of Fig. 1; Fig. 3 is an enlarged detail view of a modified form of support rod for the filament; and

Fig. 4 is an enlarged sectional view of a modified form of supporting the filament support rod.

In ordinary incandescent lamps which are extensively in use at the present time a coiled fila- '.0 ment is usually supported upon two metallic supports which are connected to the ends of the filament and which also form the leading-in conductors therefor. Where long filaments are used the filament is supported throughout its 35 length at a plurality of points by means of fine wires of molybdenum or other refractory metal which are sealed in a glass bead mounted on a stem which extends upwardly through the center of the lamp. In such a lamp one of the lead 40 wires or support rods is always at a higher potential than portions of the filament due to the resistance of the filament and if there is any emission of electrons from the heated filament these find their way to the support rods thus 45 raising the temperature of the support rod where the electrons strike. .If the temperature of the support rod becomes high enough so that it too will emit electrons these electrons will apparently return to the filament again causing the fila- 50 ment to be raised in temperature at a certain spot. This in turn increases the emission from that spot so that the filament and support rod begin to bombard each other with electrons with the result that the spot on the filament wears 55 away and becomes thinner and thinner and therefore increases in temperature and finally the filament burns out. It is the purpose of the present invention to provide a means to prevent bombardment of the filament from the support rods no matter how highly heated they may be- 6 come.

Referring now more specifically to Fig. 1 of the drawing a lamp is shown having a suitable envelope ll) of glass or other transparent material having the usual press II for supporting 10 the elements of the lamp. A support rod l2 of nickel or other metal is sealed in the press H and connected to a leading-in wire l3. Similarly a second support rod I4 is sealed in the press H and connected to the leading-in wire IS. A 15 relatively heavy carbon post I6 is attached to the support rod i2 and a second carbon post I1 is attached to the support rod l4.

These posts may be attached to the support rods in any desired way. One way of accomplish- 20 ing this purpose is to copper-plate and then nickel-plate the lower end of each of the carbon posts It and I1 and weld them to nickel sleeves l8 and I9 respectively which may be then welded to the support rods l2 and I4 forming a rigid 5 support for the carbon posts. A filamentary resistance wire 20 of tungsten or other refractory material and shown for purposes of illustration as a closely wound coil may be secured to the upper end of the carbon posts l6 and I1 by any suitable means as by a paste 2| formed of powdered carbon, tungsten, or tantalum carbide and a suitable binder which makes a rigid conductive connection. Such a paste is well known in the art for securing carbon filaments in lamps.

The filament 20 may be curved in the form of a circle, as is the usual practice, and supported upon three pigtails 22 which may be sealed in a glass bead 23 supported on a glass stem 24 which is formed integral with the press H.

The nickel support rods 12 and I4 and the sleeves I 8 and I9 should be preferably coated with an insulating material 25 so as to completely insulate the nickel supports and the mountings of the carbon rods from the inside of the bulb. The

insulating material 25 is preferably an oxide such as aluminum oxide which is prepared from anhydrous aluminum oxide and a suitable binder. With the construction as described above the filament 20 is energized similarly to the standard lamp now in general use with the exception that there is a resistance drop in each of the carbon posts I 6 and I! so that the resistance of the filament would be slightly less per the line voltage than in the usual lamp. Inasmuch as carbon is a very poor electron emitter there will be practically no bombardment oi electrons from the carbon posts I. and I1 tow the filament even though the filament should emit electrons which 5 would bombard the carbon posts and raise the temperature thereof. As the bombardment can only be in one direction the tendency is to prevent any localization of discharge between the filament and the support posts with the result that the filament is not subjected to hot spots which gradually bring about disintegration and burning out of the filament.

While carbon posts l6 and I l are illustrated in Fig. 1 it may be desirable to make these posts of metal, as the metal rod 26 shown in Fig. 3, and then to carbonize the surface of the rod so that a carbon surface 21 is provided. This will have the same effect as the carbon rods liand I! in so far as the bombarding of electrons from the Iods to the filament is concerned but the ballasting or surge arrester eilect will of course not be present.

Another way of supporting the posts l6 and I1 25 is illustrated in Fig. 4 where the nickel support rod 28 is shown with its upper end wound in a coil 29 into which the carbon post It may be inserted. If the lower end of the carbon post is copper-plated and nickel-plated, as mentioned 30 above, the carbon rod may be welded to the nickel coil which insures a good electrical contact, or a suitable carbon paste similar to that mentioned above may be used. This connection should ofcourse also be coated with the insulating material 35 similarly to the construction of Fig. l.

The invention is applicable to lamps in which the filament operates in a vacuum or with gas filled lamps as well, it being perhaps more advantageous with the latter as there is a greater tendency for a discharge to occur between the s filament and the support rod. Also it is understood that the showing of the circular formed filament is merely illustrative as the invention is applicable also to lamps in which the filament assumes any desired configuration such as the strung type of lamp.

Many other modifications of the invention may be resorted to without departing from the spirit thereof and I do not desire to limit myseli to what has been shown and described except as such limitations occur in the appended claims.

What I claim and desire to secure by Letters Patent is:

1. In a device of the class described a press, a 20 pair of support rods mounted on said press, a pair of carbon coated posts mounted on said support rods, an insulating coating covering the surface of said support rods, and a metal surfaced lighting filament connected between the free ends 25 oi. said carbon coated posts.

2. In an electric lamp a press, a pair of support rods mounted on said press, a pair of metal posts mounted on said support'rods and having the surfaces thereof carbonized, an insulating coating on the surface of said support rods, and a metal surfaced filament between the free ends 01' said posts.

CHESTER H. BRASELTON. 

